The present invention relates to technology for data access processing carried out between a host computer and a storage device, in a computer system comprising a host computer and a storage device.
Computer systems for managing large volumes of electronic data include computer systems having a host computer and a storage device, as typified by a disk array device. In a computer system, a secondary volume is defined with respect to the logical volume in the storage device (primary volume), as a provision against loss of data, or the like, and processing is implemented for managing the primary volume and the secondary volume as a pair.
Conventionally, in a computer system having a host computer and a storage device, a pair splitting technique is known whereby the defined pair of a primary volume and a secondary volume is split at a desired point in time (for example, Japanese Patent Laid-open No. 2003-316522). By splitting the pair in this way, it is possible to obtain a copy of the primary volume at the time of splitting, in the form of the secondary volume. Moreover, by using the split secondary volume, it is possible to perform back up (on-line back up) whilst an application program using the primary volume is still operating.